1. Field
This disclosure relates to techniques (e.g., apparatuses, systems and methods) for performing wellsite operations. More particularly, this disclosure relates to techniques for compensating for downhole conditions, such as pressure.
2. Related Art
Oil rigs are positioned at wellsites to locate and gather valuable downhole fluids, such as hydrocarbons. Various oilfield operations are performed at the wellsites, such as drilling a wellbore, performing downhole testing and producing downhole fluids. Downhole drilling tools are advanced into the earth from a surface rig to form a wellbore. Drilling fluids, such as drilling muds, are often pumped into the wellbore as the drilling tool is advanced into the earth. The drilling muds may be used, for example, to remove cuttings, to cool a drill bit at the end of the drilling tool and/or to line a wall of the wellbore.
During wellsite operations, measurements are often taken to determine downhole conditions. In some cases, the drilling tool may be removed so that a downhole tool may be lowered into the wellbore to take additional measurements of the wellbore. The downhole measurements may be taken by drilling, testing, production and/or other tools for determining downhole conditions and/or to assist in locating subsurface reservoirs containing valuable hydrocarbons. Such wellsite tools may be used to measure downhole parameters, such as pressure, temperature, permittivity, resistivity, etc. Such measurements may be useful in directing oilfield operations and/or for analyzing downhole conditions.
Various techniques have been developed for measuring downhole parameters as described, for example, in U.S. Pat. Nos. 7,073,609, 7,062,959 and 7,242,194. As the downhole tool advances into the earth, conditions may become increasingly harsh. In some cases, pressures and/or temperatures may rise to levels that affect the operation of downhole devices, such as sensors. Some techniques have been developed for protecting downhole devices from various downhole conditions as described, for example, in U.S. Pat. Nos. 6,997,258, 7,562,580 and 7,832,276.
Some techniques for protecting sensors may involve providing an interface, such as a bellows or piston between the sensor and wellbore fluids to protect the sensors from the harsh conditions. However, exposure to wellbore fluids may result in damage to the sensors and/or the interface, and/or degraded performance of the sensors.
Despite the advancements in downhole measurement and/or imaging tools, there remains a need for techniques to protect downhole devices from downhole conditions, such as pressure and/or exposure to downhole fluids. This disclosure is direct at providing such protection.